1. Field of the Invention
This invention relates to the chemical arts. In particular, this invention relates to distillate fuels, such as diesel fuels, containing boric acid.
2. Discussion of the Related Art
Diesel fuels find wide-spread use in diesel-powered engines. It is an advantage of such engines that they provide relatively high fuel economy. Such fuels normally contain up to as much as 40,000 ppm sulfur. The sulfur imparts several desirable properties to the fuels. For example, sulfur provides lubricity and the sulfur in diesel fuel provides for diesel fuel's ability to reduce wear on the contacting metal surfaces, particularly the fuel pumps and injectors, found in diesel-powered engines. However, sulfur suffers from serious disadvantages. It causes environmental problems in the form of high levels of sulfur dioxide and hazardous particulates in engine exhaust gases. Because of high sulfur dioxide and particulate emissions, diesel-powered engines are not widely used or permitted in many large cites.
Consequently, it is a desideratum to develop low-sulfur distillate fuel compositions and, in particular, low-sulfur diesel fuel compositions. For example, low-sulfur No. 2 diesel fuel currently contains about 500 ppm sulfur and numerous attempts have been made to further reduce the sulfur content to about 300 ppm sulfur or less. Unfortunately, removing the sulfur reduces the lubricating capacity of the diesel fuel, accelerating wear and adversely affecting fuel economy.
Boric acid is environmentally safe, inexpensive, and has an unusual capacity to enhance the antifriction and antiwear properties of sliding metal surfaces. Boric acid is a crystalline compound, insoluble in hydrocarbons such as distillate fuels. Various attempts have been made to form stable fuel compositions containing boric acid. For example, U.S. Pat. No. 6,783,561 to Erdemir discloses fuel compositions containing only about 30 to about 3000 ppm boric acid. The patent teaches that the boric acid should be in the form of nanometer-sized particles to form a stable fuel composition. U.S. Pat. No. 6,368,369, to Sanduja et al., discloses a liquid hydrocarbon fuel graft polymer-stabilized boric acid product, which can be used to make liquid hydrocarbon fuel concentrates, as well as subsequently blended to make a liquid hydrocarbon fuel containing boric acid.
However, there remains a need for stable boric acid containing distillate fuel compositions which reduce the wear and increase the fuel economy of diesel and other distillate fuel-powered engines. There remains a further need for distillate fuel concentrates that can be readily blended to make such distillate fuels. The invention meets these needs and provides related advantages as well.